tinyscram

Minimal, sync SCRAM-SHA-256 state machine (RFC 5802 / RFC 7677) for server and client roles. No I/O, no async — consumers supply the framing (SMTP/IMAP SASL, PostgreSQL AuthenticationSASLContinue envelopes, whatever else).

Server-side credentials follow RFC 5802 §3: (salt, iterations, StoredKey, ServerKey). No plaintext password ever held.

Server

use tinyscram::{Credential, ServerSession, peek_authcid};

let authcid = peek_authcid(client_first_bytes)?;
let credential: Credential = lookup_credential(authcid).await?;

let mut session = ServerSession::new(credential);
let server_first = session.handle_client_first(client_first_bytes)?;
// send server_first, receive client_final
let server_final = session.handle_client_final(client_final_bytes)?;
// send server_final, authentication complete

Client

use tinyscram::ClientSession;

let mut session = ClientSession::new("alice", "secret");
let client_first = session.client_first();
// send client_first, receive server_first
let client_final = session.handle_server_first(server_first_bytes)?;
// send client_final, receive server_final
session.handle_server_final(server_final_bytes)?;

Credential provisioning

use tinyscram::crypto::DerivedKeys;

let salt: [u8; 16] = rand::random();
let keys = DerivedKeys::from_password("user-password", &salt, 4096);
// Store (salt, 4096, keys.stored_key, keys.server_key); discard keys.client_key.

Channel binding

The GS2 parser recognises n / y / p=<type>, but ServerSession currently rejects p= (non-PLUS only). The Gs2Header API is exposed so SCRAM-SHA-256-PLUS can be added without breaking changes.

License

Apache-2.0.